"The model does not explicitly show the equations used in
the model, and source code is not accessible. The model does, however, state
the integration methods available in the solution, as well as the method of
force calculation between gravitationally bound objects. The user has control
over one approximation parameter, the shield radius, which is described in the
"Sample files were included with the program. Many of these
were meant to be used with lesson plans packaged with the program that included
expected solutions, so it was possible to compare a pre-created input file with
"Tests of the software's ability to run on the specified
platforms were made on both Windows and Macintosh.
For each integration method, the default time steps for default models
resulted in little problems with conserving energy and momentum.
Decreasing the time step did not result in substantial changes in the
result, whereas an increased time step did cause error to occur. This is
to be expected with models that use explicit integration methods.
"Exact comparisons of the Windows and Mac models were not possible, as the
shield radius was handled in a slightly different way between the two versions.
When the model for Mac was run against the model for
Windows, the model results were practically identical, after the shield
modification discrepancy was taken into account.
"In summary, this model did not include enough information
about the base assumptions of the model or how they are implemented as code to
directly apply verification tests, and one must rely on symptomatic tests.
Examples are provided, the code runs on the stated platforms without obvious
problems, and when the code is run with the default approximation parameters
there are no obvious physical impossibilities.